Outdoor Unit for Air Conditioner

ABSTRACT

An air conditioner outdoor unit including a box-shaped casing for accommodating at least a heat exchanger, an air blower, and a compressor. The casing has a front wall with an opening. A reinforcement rib is arranged near the opening of the front wall to increase compressive strength in the vicinity of the opening.

TECHNICAL FIELD

The present invention relates to a casing structure for an outdoor unitfor an air conditioner.

BACKGROUND ART

An air conditioner generally includes an indoor unit arranged inside adwelling unit and an outdoor unit arranged outside the dwelling unit. Asshown in FIGS. 15 and 16, the outdoor unit includes a box-shaped casing1. A partition plate 2 partitions the space in the casing 1 into amachine compartment 1A and a fan compartment 1B. A compressor 3 and areceiver 4 are arranged in the machine compartment 1A, and a heatexchanger 5 and an air blower 6 are arranged in the fan compartment 1B.

Air inlets 7 are formed in the front and side surfaces of the casing 1.Air outlets 8 are formed in the rear surface of the casing 1. An opening9 used for maintenance is formed in the lower end of the casing 1, and acover 9 a is attached to the casing 1 to cover the opening 9 (refer to,for example, patent document 1).

[Patent Document 1] Japanese Laid-Open Patent Publication No.2003-106565 DISCLOSURE OF THE INVENTION

Prior to shipment, the outdoor unit is stored in a warehouse in astacked state. Thus, impacts produced when stacking the outdoor unitsand the weight of the outdoor units result in a tendency of load beingconcentrated on the front wall 11F near the opening 9 (portion X shownin FIG. 15). As a result, buckling deformation may occur near theopening 9 of the front wall 11F when stacking outdoor units.

The front wall 11F is a component that is separate from a frame body11R, which forms the rear surface of the casing 1, and a frame plate11Y, which is arranged near the air inlets 7. The front wall 11F has anL-shaped cross-section and is partially narrowed near the opening 9.Thus, the rigidity of the front wall 11F is partially low near theopening 9. As a result, compressive load that is produced duringstacking tends to cause buckling deformation occurring near the opening9 of the front wall 11F. For the above reasons, it is required thatcompression rigidity be increased near the opening 9 of the front wall11F so that buckling deformation does not occur when stacking theoutdoor units.

However, patent document 1 only disclosed a structure for increasing thestrength of a curved portion of the partition plate and does notdisclose a structure for increasing the strength of the front wall ofthe casing.

It is an object of the present invention to provide an outdoor unit forair conditioner that increases the compression rigidity near the openingin the front wall with a reinforcement rib and minimizing bucklingdeformation caused by compressive load.

In order to solve the above problems, a first aspect of the presentinvention provides an air conditioner outdoor unit including abox-shaped casing for accommodating at least a heat exchanger, an airblower, and a compressor. The casing has a front wall with an opening. Areinforcement rib is arranged near the opening of the front wall toincrease compressive strength in the vicinity of the opening.

With such a structure, the reinforcement rib increases the compressionrigidity of the front wall near the opening. Thus, deformation caused bycompressive load is less likely to occur near the opening of the frontwall when stacking outdoor units.

In the air conditioner outdoor unit, it is preferred that thereinforcement rib extend in the vertical direction. In this case, thereinforcement rib increases the compression rigidity of a thin platethat forms the casing. This effectively suppresses deformation caused bya compressive load.

In the air conditioner outdoor unit, it is preferred that thereinforcement rib extends upward from the side of the opening and alongthe edge of the opening. This entirely and effectively reinforces thevicinity of the opening. Thus, the compression rigidity near the openingof the front wall increases, and deformation caused by compressive loadis further suppressed.

In the air conditioner outdoor unit, it is preferred that the length ofthe reinforcement rib be set in accordance with the height of theopening. In this case, the reinforcement rib moves the area in whichbuckling stress concentrates to above the opening of the front wall.Thus, concentration of buckling stress in the front wall at the vicinityof the opening is avoided, and deformation caused by compressive load isfurther suppressed.

In the air conditioner outdoor unit, it is preferred that a plurality ofreinforcement ribs are arranged parallel to each other. In this case,each reinforcement rib increases the reinforcement effect near theopening of the front wall. Thus, compression rigidity of the front wallnear the opening further increases, and deformation caused bycompressive load is further suppressed.

In the air conditioner outdoor unit, it is preferred that thereinforcement rib is formed by pressing part of the front wall so as tohave a U-shaped cross-section. This simultaneously and easily forms thereinforcement rib with the front wall when manufacturing the casing.This lowers the manufacturing cost of the product.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing the entire structure of an airconditioner outdoor unit according to a first embodiment;

FIG. 2 is a perspective view showing a front wall of a casing;

FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. 2;

FIG. 4 is a partial plan view showing the vicinity of an opening in thefront wall;

FIG. 5 is a front view showing the front wall;

FIG. 6 is a front view showing the front wall with a plurality ofreinforcement ribs;

FIG. 7 is a front view showing a front wall for an air conditioneroutdoor unit according to a second embodiment;

FIG. 8 is a front view showing a modification of the reinforcement rib;

FIG. 9 is a front view showing a first sample (first analysis example)of the front wall;

FIG. 10 is a front view showing a second sample (second analysisexample) of the front wall;

FIG. 11 is a front view showing a third sample (third analysis example)of the front wall;

FIG. 12 is a factor effect diagram for analyzing the reinforcementeffects of the reinforcement ribs in the first and the secondembodiments;

FIG. 13 is a graph showing the relationship between the rib length andthe buckling load;

FIG. 14 is a graph showing the relationship between the rib position andthe buckling value;

FIG. 15 is a perspective view showing the entire structure of an outdoorunit for an air conditioner in the prior art; and

FIG. 16 is a cross-sectional view showing the internal structure of theoutdoor unit.

BEST MODE FOR CARRYING OUT THE INVENTION FIRST EMBODIMENT

An air conditioner outdoor unit according to a first embodiment of thepresent invention will now be described with reference to FIGS. 1 to 6.

As shown in FIG. 1, the air conditioner outdoor unit includes agenerally box-shaped casing 1. A pair of air inlets 7 are formed in thefront surface of the casing 1, and air outlets (not shown) are formed inthe rear surface. The inlets 7 are respectively formed at an upper partand a lower part of the casing 1.

The front surface of the casing 1 includes a frame plate 11Y arrangednear the air inlets 7, and a front wall 11F having an L-shapedcross-section. A frame body 11R having a U-shaped cross-section andforming the rear surface of the casing 1 is attached to the rear part ofthe frame plate 11Y and the front wall 11F. An opening 9 used formaintenance is formed at the lower end of the casing 1, and a cover 9 ais attached to the casing 1 so as to cover the opening 9. The opening 9is formed by cutting out a corner of the front wall 11F and the framebody 11R. Thus, the front wall 11F is defined into a lower part P1 andan upper part P2, which is wider than the lower part P1, as shown inFIG. 2. In the following description, the lower part P1 has a width ofG2, and the upper part P2 has a width of G1, as shown in FIG. 4.

The lower part P1 of the front wall 11F is narrow and planar. Thus, thestrength (compressive strength) is low against compressive load. Thus,buckling deformation is likely to occur near the opening 9 of the lowerpart P1 of the front wall 11F, in particular, at portion X shown in FIG.15 due to the impact produced during stacking and the weight of theoutdoor unit (about 90 kg in a case of trunk type).

In the present invention, a reinforcement rib 10 for increasing thecompressive strength is arranged at the lower part P1 of the front wall11F. The reinforcement rib 10 is extending linearly in the verticaldirection along the side edge of the opening 9. As shown in FIGS. 3 and4, the reinforcement rib 10 has a U-shaped cross-section and projectstoward the front from the front wall 11F. The reinforcement rib 10increases the bending rigidity of the front wall 11F near the opening 9.In the following description, the reinforcement rib 10 has a width of A,a depth of B, and a length of C.

The reinforcement rib 10 is spaced laterally from the side edge of theopening 9 by distance D. The length C of the reinforcement rib 10corresponds to the height H of the opening 9. The length C, whichcorresponds to the height H of the opening 9, is a value obtained byadding the length of distance E from the upper end of the opening 9 tothe length from a position separated upward by distance F from the lowerend of the opening 9 to the upper end of the opening 9. The length Ccorresponding to the height H of the opening 9 may be the length from aposition separated upward by distance F to the upper end of the opening9.

The reinforcement rib 10 moves the region of stress concentration, whichresults from compressive load, from the lower part P1 to the upper partP2 of the front wall 11F. Thus, the concentration of stress at thevicinity of the opening 9 of the front wall 11F is avoided. As a result,buckling deformation caused by compressive load is less likely to occurnear the opening 9 of the front wall 11F even when stacking outdoorunits.

As shown in FIG. 5, it is preferred that the distance E from the upperend of the opening 9 to the upper end of the reinforcement rib 10 be setto be longer than as shown in FIG. 4. In this case, the compressivestrength is increased not only at location X (see FIG. 15) at whichbuckling deformation is likely to occur but also in a wide range nearthe opening 9 of the front wall 11F.

The reinforcement rib 10 is formed to have a U-shaped cross-section bypressing part of the front wall 11F of the casing 1. In this case, thereinforcement rib 10 is easily formed at the same time as when formingthe front wall 11F when manufacturing the casing 1.

The first embodiment has the advantages described below.

(1) The compressive strength near the opening 9 of the front wall 11F isgreatly increased.

(2) Since the compressive strength near the opening 9 of the front wall11F is increased, more products may be stacked together for storage.This increases the efficiency of a warehouse. Further, bucklingdeformation resulting from compressive load is less likely to occur nearthe opening 9 of the casing 1 when delivering the products.

(3) The compressive strength near the opening 9 of the front wall 11F isincreased. Thus, the plate thickness of the front wall 11F may bedecreased to 0.7 mm to 0.6 mm. This reduces the used material and lowersthe material cost reduces. Furthermore, the formation quality of theproduct may be improved.

(4) Since the compressive strength near the opening 9 of the front wall11F is increased, the used amount of material for packaging the productmay be reduced.

SECOND EMBODIMENT

An air conditioner outdoor unit according to a second embodiment of thepresent invention will now be described with reference to FIG. 7 andFIG. 8. Detailed description of portions in the second embodiment thatare similar to the first embodiment will be omitted.

As shown in FIGS. 7 and 8, a reinforcement rib 10, which extends alongthe side edge of the opening 9, includes an upper end portion extendingalong the corner of the opening 9. The reinforcement rib 10 increasesthe bending rigidity of the front wall 11F near the opening 9.

Unlike the first embodiment, in the reinforcement rib 10 shown in FIG.7, the upper end portion of the reinforcement rib 10 is curved along thecorner of the opening 9. In the reinforcement rib 10 shown in FIG. 8,the upper end portion of the curved reinforcement rib 10 extendslaterally along the upper side edge of the opening 9. The reinforcementrib 10 reinforces most of the opening 9 in the front wall 11F.

The reinforcement effect in the case of FIG. 7 is assumed to be the sameas the first embodiment, and the reinforcement effect in the case ofFIG. 8 is assumed to be higher than in the case of FIG. 7.

(Study of Reinforcement Effect)

In relation to the reinforcement rib 10 of the first embodiment (seeFIGS. 1 to 6) and the reinforcement rib 10 of the second embodiment (seeFIGS. 7 and 8), an arcuate reinforcement rib 10 arranged only at thecorner of the opening 9 as shown in FIG. 9 was used as a first sample.That in which the upper end of A reinforcement rib 10 that laterallyextends the upper end of the reinforcement rib 10 of FIG. 9 along theupper side edge of the opening 9 as shown in FIG. 10 used as a secondsample. Furthermore, a reinforcement rib 10 (lateral rib) extending inthe lateral direction along the upper side edge of the opening 9 asshown in FIG. 11 was used as a third sample. The reinforcement effectsby the reinforcement rib 10 of the first and the second embodiments werestudied from the standpoint of quality engineering including comparisonamong first to third samples.

(Influence of Dimension and Position of the Reinforcement Rib 10 on theCompressive Strength)

First, the reinforcement effect of the reinforcement rib 10 of the firstembodiment was studied.

During the study, the dimensions (width A, depth B, length C of FIG. 3and FIG. 4) and the position (distance D in FIG. 4) of the reinforcementrib 10 were assumed as design variables (evaluation parameters), andthree patterns (standard values 1 to 3) were set for standard values ofeach design variable. The design variable and each standard value areshown in table 1. The standard values 1, 2, 3 of each design variable Ato D were allocated to an L9 orthogonal experiment table of table 2. Thebuckling load (kgf) for when stacking the outdoor units were obtainedfor analyses No. 1 to No. 9 in which the standard values were combined.The results are shown in table 2.

TABLE 1 Rib Dimension and Standard value Position (mm) 1 2 3 A (Width)4.0 5.0 6.0 B (Depth) 1.0 1.5 2.0 C (Length) 100.0 142.0 184.0 D(Distance) 48.0 33.0 18.0

TABLE 2 Analysis Combination of Standards Buckling No. A B C D Load(kgf) 1 1 1 1 1 545.3 2 1 2 2 2 616.0 3 1 3 3 3 721.2 4 2 1 2 3 595.9 52 2 3 1 642.4 6 2 3 1 2 624.1 7 3 1 3 2 621.3 8 3 2 1 3 624.1 9 3 3 2 1703.6 No Ribs 524.2

Table 3 is a dispersion analysis table for the calculation results oftable 2. Table 4 is a dispersion analysis table for a residual group.

TABLE 3 Source S f V F0 S′ P (%) A 0.2678 2 0.1339 0.2678 6.38 B 2.55852 1.2793 2.5585 60.92 C 1.1931 2 0.5966 1.1931 28.41 D 0.1805 2 0.09030.1805 4.30 e 0 0 0 — 0 0 T 4.1999 8 4.1999 100.00

TABLE 4 Source S f V F0 S′ P (%) A 0.2678 2 0.1339 1.48 0.0873 2.08 B2.5585 2 1.2793 14.17 2.378 56.62 C 1.1931 2 0.5966 6.61 1.0126 24.11 e0.1805 2 0.0903 — 0.722 17.19 T 4.1999 8 4.1999 100.00

FIG. 12 is a factor effect diagram of each design variable A to D. InFIG. 12, the vertical axis indicates the SN ratio, and the horizontalaxis indicates the design variable (A(width), B(depth), C(length),D(distance) from the left). In the factor effect diagram, thereinforcement effect increases as the SN ratio increases, and the degreeof contribution to the reinforcement effect increases as the inclinationof the design variable increases. Table 5 shows the SN ratiocorresponding to each standard value (1-3) of each design variable.

TABLE 5 Design Variable Standard value (Factor) Title 1 2 3 A (Width)55.8956 55.8548 56.2394 B (Depth) 55.3576 55.9510 56.6712 C (Length)55.5146 56.0808 56.3945 D (Distance) 55.9454 55.8546 56.1899

From the factor effect diagram of FIG. 12, the predicted value of the SNratio is 57.5051 dB, or 749.9 kgf when converted to the buckling loadvalue, under the optimum condition in which the standard values of eachdesign variable at which the SN ratio becomes maximum are combined. Thecalculated value (analytic value) of the buckling load when the optimumstandard values are combined is 741.3 kgf, which is substantially thesame as the predicted value of the SN ratio. According to this result,the result obtained using the orthogonal table was verified as beingcorrect and reliable. The predicted value and the analytic value areshown in table 6.

TABLE 6 Analytic Value Predicted value (Study) SN Ratio (dB) Load Value(kgf) Load Value (kgf) 57.5051 749.9 741.3

The followings are apparent from the above result.

(1) A large reinforcement effect is obtained by the reinforcement rib(vertical rib) extending in the vertical direction.

(2) The depth B of the reinforcement rib 10 contributes the most, andthe length C of the reinforcement rib 10 contributes the next most tothe reinforcement effect. The contribution to the reinforcement strengthof the width A and the spaced distance D of the reinforcement rib 10 areboth small. However, if the reinforcement rib 10 is too deep, theformation quality and the outer appearance quality of the product may bedecreased. Due to such reasons, the depth B of the reinforcement rib 10is preferably between 1.0 mm and 3.0 mm, and the width A of thereinforcement rib 10 is preferably between 4.0 mm and 6.0 mm.

(3) Since the length C of the reinforcement rib 10 also greatlycontributes to the reinforcement effect, a large reinforcement effect isobtained by elongating the reinforcement rib 10.

According to such results, the reinforcement rib 10 shown in FIGS. 1 to4 of the first embodiment is effective in increasing the compressivestrength, and the reinforcement rib 10 shown in FIG. 5 is furthereffective in increasing the compressive strength. Furthermore, it can beeasily assumed that a greater reinforcement effect is obtained byarranging two reinforcement ribs 10 in parallel as shown in FIG. 6.

The reinforcement effect of one vertical rib and the reinforcementeffect of two vertical ribs were then compared. A case in which therewas only one vertical rib is represented by (S1) (see FIG. 1 to FIG. 5),a case in which there are two vertical ribs is represented by (S2) (seeFIG. 6), and a case in which there is only the horizontal rib isrepresented by (S3) (see FIG. 11). The buckling load (kgf) of when thelength C of each reinforcement rib 10 was 0 mm, 100 mm, 142 mm, 184 mm,226 mm, and 268 mm was respectively obtained for (S1) to (S3). Theresults are shown in table 7.

TABLE 7 Length of rib (mm) 0.0 100.0 142.0 184.0 226.0 268.0 Buckling S1524.2 618.9 675.0 741.0 848.8 852.6 Load S2 524.2 — — — 1002.4 — (kgf)S3 524.2 542.0 580.0 634.5 672.2 —

The relationship between the length of the rib and the buckling load wasrespectively obtained for (S1) and (S3). The results are shown in thegraph of FIG. 13.

From the graph of FIG. 13, the reinforcement effect of the vertical ribwas found to be higher than the reinforcement effect of the horizontalrib. Furthermore, the reinforcement effect of two vertical ribs wasfound to be higher than the reinforcement effect of one vertical ribfrom the result of table 7. Moreover, the reinforcement effect was foundto increase as the length of the rib increases in the case of thevertical rib. The reinforcement effect of the horizontal rib was foundto be higher, although slightly, when the rib length became greater thanor equal to a predetermined dimension.

Similar effects are obtained by the reinforcement rib 10 of FIG. 9 andthe reinforcement rib 10 of FIG. 10. In the case of the reinforcementrib 10 of FIG. 11, the reinforcement effect was found to become higheras the rib became longer, or the rib portion corresponding to the lowerpart P1 of the front wall 11F became longer.

From the above results, the bending rigidity in the vertical directionand the horizontal direction are both increased, and thus thecompressive strength is further effectively increased by thereinforcement rib 10 of FIG. 7 that combines the reinforcement rib 10 ofFIG. 1 to FIG. 5 and the reinforcement rib 10 of FIG. 9 or thereinforcement rib 10 of FIG. 8 that combines the reinforcement rib 10 ofFIGS. 1 to 5 and the reinforcement rib 10 of FIG. 10.

The reinforcement rib 10 of FIG. 7 shown in the second embodiment isrepresented by (S4), the reinforcement rib 10 of FIG. 8 is representedby (S5), the reinforcement rib 10 of FIG. 9 is represented by (S6), andthe reinforcement rib 10 of FIG. 10 is represented by (S7). The bucklingloads (kgf) for (S4) to (S7) were respectively obtained. The results areshown in table 8 along with the case for no ribs.

TABLE 8 Rib Arrangement None S6 S4 S7 S5 Buckling 524.2 543.6 706.7562.9 831.7 Load (kgf)

From the results of table 8, a large reinforcement effect was obtainedfor (S4) and (S5). Although small, a reinforcement effect was obtainedfor (S7). However, sufficient reinforcement effect was not obtained for(S6).

With regarding to the reinforcement ribs 10, 10 a, 10 b of FIG. 1 toFIG. 6 and the reinforcement rib 10 of FIG. 7 and FIG. 8, the distance Dfrom the opening 9 is set to an appropriate dimension from the ratiowith respect to the width G2 of the lower part P1 of the front wall 11Fso as to obtain compressive strength that is greater than or equal to apredetermined value.

FIG. 14 is a graph showing a relationship between the width G2 of thelower part P1 of the front wall 11F and the spaced distance D from theopening 9 of the reinforcement rib. From the graph of FIG. 14,sufficient compressive strength was found to be obtained by setting thedistance D in the range of 5% to 40% of the width G2 of the lower partP1 of the front wall 11F.

Furthermore, when the width G2 of the lower part P1 of the front wall11F is narrower than the width A of the opening 9 (black circle in FIG.14), the range of the ratio (D/G2) of the width G2 and the distance D atwhich the reinforcement effect is sufficient was found to be narrowerthan when the width G2 is the same or greater than the width W of theopening 9 (square or triangle of FIG. 14). The reinforcement effect wasalso found to significantly lower when the width G2 is constant and thespaced distance D is reduced.

If the reinforcement effect is small, the buckling position exists atthe lower part P1 of the front wall 11F adjacent to the opening 9 in thesame manner as the case of no rib shown in FIG. 15. However, if thereinforcement effect is large, the buckling position moves above thereinforcement rib 10, that is, to the upper part P2 of the front wall11F having a width that is wider than the lower part P1.

(General Overview of the Results of the Study)

(1) The reinforcement effect of the horizontal rib is extremely limitedcompared to the reinforcement effect of the vertical rib in thereinforcement ribs 10, 10 a, and 10 b. Thus, the reinforcement effectfurther increases by combining the horizontal rib and the vertical rib.

(2) When the length of the vertical rib is greater than or equal to theheight H of the opening 9, deformation due to the compressive load iseffectively suppressed compared to when the length is less than theheight H of the opening 9. Therefore, it is preferable that the lengthof the vertical rib be longer than the height H of the opening 9.

(3) The reinforcement effect is barely obtained when the length of thehorizontal rib is the same as the width W of the opening 9. However, thereinforcement effect further increases if the length of the horizontalrib is longer than the width W of the opening 9. Thus, the length of thehorizontal rib is preferably longer than the width W of the opening 9.

(4) The reinforcement effect is barely obtained even if an arcuatereinforcement rib is arranged at the corner of the opening 9. However,the reinforcement effect further increases by combining thereinforcement rib and the vertical rib.

(5) The compressive strength during stacking is greatly increased when aplurality of vertical ribs are arranged under the above conditions.

1. An air conditioner outdoor unit including a box-shaped casing (1) foraccommodating at least a heat exchanger (5), an air blower (6), and acompressor (3), wherein the casing (1) has a front wall (11F) with anopening (9), the outdoor unit being characterized by: a reinforcementrib (10), (10 a), (10 b) arranged near the opening (9) of the front wall(11F) to increase compressive strength in the vicinity of the opening(9).
 2. The air conditioner outdoor unit according to claim 1,characterized in that the reinforcement rib (10), (10 a), (10 b) extendsin a vertical direction.
 3. The air conditioner outdoor unit accordingto claim 1 or 2, characterized in that the reinforcement rib (10), (10a), (10 b) extends upward from a side of the opening (9) and along anedge of the opening (9).
 4. The air conditioner outdoor unit accordingto claim 2, characterized in that the reinforcement rib (10), (10 a),(10 b) has a length set in accordance with height of the opening (9). 5.The air conditioner outdoor unit according to claim 1, characterized by:a plurality of reinforcement ribs (10 a, 10 b) arranged parallel to eachother.
 6. The air conditioner outdoor unit according to claim 1,characterized in that the reinforcement rib (10), (10 a), (10 b ) isformed by pressing part of the front wall (11F) so as to have a U-shapedcross-section.